I always use medic animal website, I purchase all my flea, tick, worming products from there and they are superb. Much cheaper than vet prices and are delivered very quickly too. Apologies, I didn't look at the website you gave and am assuming these products are being sold cheap...?
I would most definately take a look at the website that I use, it maybe of some use to you? It is definately cheaper than the prices that you have listed.
Our vets are so reasonable in their charges and thoroughly competent so I dont begrudge the markup on the worming tablet. Ticks I do for friend's dogs and we never had a dog with fleas.